Methanol oxidation on carbon-supported PtSn electrodes in silicotungstic acid

• Published in: Electrochimica acta Vol. 39; no. 5; pp. 691 - 700
• Main Authors: Aricò, A.S., Kim, H., Shukla, A.K., Ravikumar, M.K., Antonucci, V., Giordano, N.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.1994; Elsevier
• Subjects: ac impedance spectroscopy; Chemistry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Kinetics and mechanism of reactions; methanol oxidation; porous-carbon electrodes; PtSn catalyst; silicotungstic acid; porous-carbon electrodes; PtSn catalyst; methanol oxidation; ac impedance spectroscopy; silicotungstic acid; Experimental study; Carbon; Porous material; Electrodes; Platinum; Concentration effect; Adsorbed state; Tin; Oxidation; Electrochemical reaction; Catalyst activity; Electrical impedance; Modified material; Methanol
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/0013-4686(94)80012-X

Electro-oxidation of methanol was studied on carbon-supported PtSn/C electrodes in silcotungstic acid (SiWA) at various concentrations. The porous-carbon electrodes employing PtSn/C catalyst have been characterized using chemical analyses, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in conjunction with electrochemistry. The presence of PtSn and Pt 3Sn alloys along with Pt and SnO 2 phases in the catalyst were identified by XRD. XPS analysis showed a lower amount of PtO species in the PtSn/C catalyst with respect to the corresponding Pt/C sample. From the steady-state galvanostatic polarization data on PtSn/C electrodes in SiWA, it is inferred that a one-electron process is the rate determining step. The performance of the electrodes in 0.084 M SiWA was better than in 2.5 M H 2SO 4 under similar conditions up to load currents of about 100 mA cm −2 indicating the promoting behaviour of the electrolyte. At currents larger than 100 mA cm −2, the performance of the electrodes in 0.084 SiWA was poorer than that in 2.5 M H 2SO 4 mainly due to the dominance of mass polarization in the former owing to the large size of keggin units associated with the structure of SiWA. This aspect was supported by cyclic voltammetry and ac impedance studies on PtSn/C electrodes. Simulation of the electrochemical impedance response for the oxidation of methanol in SiWA was carried out using the equivalent electrical circuit model.